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Datasheet

Sepedomerus macropus (liverfluke snail predator fly)

Summary

  • Last modified
  • 04 October 2017
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Sepedomerus macropus
  • Preferred Common Name
  • liverfluke snail predator fly
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Uniramia
  •         Class: Insecta
  • Summary of Invasiveness
  • Sepedomerus macropus, commonly known as liverfluke snail predator fly, is a species of marsh fly, otherwise known as a snail-killing fly. It can be up to 8 mm long with tawny brown and black colouration. Its na...
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Identity

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Preferred Scientific Name

  • Sepedomerus macropus Walker, 1849

Preferred Common Name

  • liverfluke snail predator fly

Other Scientific Names

  • Sepedon macropus Walker, 1849
  • Sepedon nigriventris Wulp, 1897

International Common Names

  • English: marsh fly; snail-killing fly; swale fly

Summary of Invasiveness

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Sepedomerus macropus, commonly known as liverfluke snail predator fly, is a species of marsh fly, otherwise known as a snail-killing fly. It can be up to 8 mm long with tawny brown and black colouration. Its native distribution is in Nearctic and Neotropical regions where it has been reported from southern Texas (USA), the eastern lowlands of Mexico, Central America, north-western South America (Colombia, Ecuador, Peru) and the Caribbean Islands to Trinidad. It inhabits marshes, swamps, ponds, canals, ditches, slow-flowing streams, and taro and watercress habitats, where its larvae attack and feed on aquatic snails. S. macropus was introduced from Nicaragua to Hawaii in 1958-59 as a biological control agent of the lymnaeid snail vectors of the liver fluke, Fasciola gigantica. The fly became well established on the major Hawaiian Islands. It has since been introduced to Guam, where it is reported to be established, and Thailand. Together with habitat loss, predation by S. macropus and another introduced sciomyzid, Sepedon aenescens, represents a significant threat to the survival of native Hawaiian lymnaeid snails, including Newcomb’s snail (Erinna newcombi), a threatened species found only in six watersheds on the island of Kauai.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Uniramia
  •                 Class: Insecta
  •                     Order: Diptera
  •                         Family: Sciomyzidae
  •                             Genus: Sepedomerus
  •                                 Species: Sepedomerus macropus

Notes on Taxonomy and Nomenclature

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Sepedomerus macropus (Walker, 1849) belongs to the dipterous family Sciomyzidae, commonly known as marsh flies or snail-killing flies (Barker et al., 2004; Knutson and Vala, 2011). The species was originally described in the genus Sepedon by Francis Walker in 1849 from specimens collected in Jamaica (Walker, 1849). Malloch (1914) synonymized Sepedon nigriventris Wulp, 1897 with Sepedon macropus (Abercrombie, 1970). Steykal first classified the Sepedon group, which included six genera, including Sepedomerus as a new genus (Steyskal, 1973). Sepedon macropus Walker, 1859 was transferred to Sepedomerus as the type species (Steyskal, 1973; Knutson et al., 1986). Eight genera are now recognized in the Sepedon group: Ethiolimnia Verbeke, Teutoniomyia Hennig, Thecomyia Perty, Sepedoninus Verbeke, Sepedonella Verbeke, Sepedon Latreille, Sepedomerus Steyskal and Sepedonea Steyskal (Marinoni and Mathis, 2006).

Description

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The life stages of S. macropus are the egg, three larval instars, a puparium and the adult. The adult male of S. macropus is described in Walker (1849) and the immature stages are described in Neff and Berg (1966). Keys to the eggs, mature larvae and puparia of species of Sepedon (including S. macropus) are given in Neff and Berg (1966) and a key to the Sepedon group (which includes Sepedomerus as a new genus) is given in Steyskal (1973).

Adults of S. macropus are 6.5-8 mm long and tawny brown and black. There is a black spot on each side of the head between the eyes and the antennae. The antennae are longer than the head. The abdomen is elliptical and the hind legs are long and tawny, with a darkened apex and a conspicuous preapical annulus on the hind femora. The wings are brown with black veins that are tawny at the base (Walker, 1849; Neff and Berg, 1966).

Newly laid eggs are cream coloured and change to light orange within 24-36 hours; they are 1.17-128 mm long and 0.34-0.37 wide. Often a dorsal depression is present at the micropylar end of the egg but this is not always present and it is therefore not reliable as a diagnostic feature (Neff and Berg, 1966; Abercrombie, 1970).

The first-instar larva is white and 1.6-4.0 mm long and 0.2-0.6 mm wide. The second-instar larva is yellowish-white, 2.8-8.7 mm long and 0.5-1.5 mm wide. There is often a prominent mid-dorsal stripe and indistinct oblique stripes dorsolaterally on segments 5 to 9. The third-instar larva is yellow or orange-white and 7.8-13.5 mm long and 1.4-3.1 mm wide, with obscure mid-dorsal and faint oblique stripes. All three larval stages have a transparent integument and paired mouthhooks. In mature larvae the accessory teeth of the mouthhooks are darkly pigmented, only slightly decurved; the anterior spiracles are not inflated distal to the stigmatic scar; and there is a pharyngeal sclerite with a pigmented area on the dorsal cornua.  

The puparium is large, 5.6-8.00 mm long and 2.5-3.2 mm wide, and can vary in colour from straw-coloured to brown-black with irregular light markings ventrally and laterally. Three accessory teeth on the mouthhooks of the cephalopharyngeal skeleton of the puparium are darkly pigmented and slightly decurved (Neff and Berg, 1966).

Distribution

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The native distribution of S. macropus is in Nearctic and Neotropical regions, where it has been reported from southern Texas (Brownsville and Val Verde), USA (Knutson et al., 1986); the eastern lowlands of Mexico (Neff and Berg, 1966); Central America (Nicaragua, Guatemala, Costa Rica) (Davis, 1959; Neff and Berg, 1966); north-western South America (Colombia, Ecuador, Peru) (Boyes et al., 1969; Neff and Berg, 1966); and the Caribbean Islands  to Trinidad (Neff and Berg, 1966; Knutson et al., 1986), including Jamaica (Johnson, 1894; Gowdey, 1926) and Puerto  Rico (Wolcott, 1936, cited in Abercrombie, 1970).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

ThailandAbsent, unreliable recordIntroducedPapp et al., 2006

North America

MexicoPresentNeff and Berg, 1966Most recent specimens 1969
USA
-HawaiiPresentIntroduced1958 Invasive Davis, 1959; Davis, 1974Introduced to and established on the major Hawaiian islands
-TexasLocalisedKnutson et al., 1986Brownsville and Val Verde: most recent specimens 1999

Central America and Caribbean

Costa RicaPresentNeff and Berg, 1966
GuatemalaPresentNeff and Berg, 1966Most recent specimens 2003
JamaicaPresentJohnson, 1894; Gowdey, 1926; Knutson et al., 1986
NicaraguaPresentDavis, 1959; Neff and Berg, 1966
PanamaPresentW.L. Murphy, unpublishedOne female from Gamboa, Panamá, found in collection at Brigham Young University, Provo, Utah; unpublished
Puerto RicoPresentWolcott, 1936, July; Abercrombie, 1970
Trinidad and TobagoPresentKnutson et al., 1986Most recent specimens 2008

South America

ColombiaPresentNeff and Berg, 1966
EcuadorPresentNeff and Berg, 1966Most recent specimens 1988
PeruPresentNeff and Berg, 1966; Boyes et al., 1969

Oceania

GuamPresentKnutson, 1962; Neff and Berg, 1966Reported to be established

History of Introduction and Spread

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S. macropus was imported from Managua, Nicaragua, to Hawaii in October 1958 for the biological control of lymnaeid snail vectors of the liver fluke Fasciola gigantica. The liver fluke has been recorded in the Hawaiian Islands since 1892 and is the causative agent of fascioliasis, one of the most important parasitic diseases of beef and dairy cattle there (Davis, 1960).

In Hawaii, S. macropus was found to be an effective predator of Fossaria viridis, a non-native snail vector of the liver fluke (Davis, 1960). S. macropus was successfully mass reared in redwood troughs outdoors, producing about 4500 flies per month (Chock et al., 1961; Knutson and Vala, 2011). Between December 1958 and December 1959, 7633 flies were released on the five major islands of the Hawaiian group and became well established on Hawaii, Maui, Oahu and Kauai Islands (Davis, 1959, 1960, 1961; Davis et al., 1961; Chock et al., 1961; Davis and Krauss, 1962; Funasaki et al., 1988; Knutson and Vala, 2011). Of the species of Sciomyzidae introduced to Hawaii, only S. macropus and Sepedon aenescens (the latter introduced from Japan in 1966 and 1967) became established (Davis, 1974; Knutson and Orth, 1984; Knutson and Vala, 2011).

S. macropus (origin unknown) was later introduced to Guam, also to control lymnaeid snail vectors of Fasciola gigantica (Knutson, 1962; Neff and Berg, 1966), and it is reported to have become established there (Beaver, 1989; Knutson and Vala, 2011).

Papp et al. (2006) reported that S. macropus was introduced to Thailand but no further details are given. Yano (1978) reported that no specimens of S. macropus have been collected from Asian paddy fields since Yano (1968) and that the species appears to be excluded from Asia.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Guam   Biological control (pathway cause) Yes No Barker et al., 2004; Knutson and Vala, 2011 Introduced in an attempt to control lymnaeid snail vectors of liver fluke (Fasciola gigantica)
Hawaii Nicaragua 1958-59 Biological control (pathway cause) Yes No Davis, 1959; Davis, 1960; Davis, 1972; Davis, 1974 Introduced in an attempt to control lymnaeid snail vectors of liver fluke (Fasciola gigantica)
Thailand   Biological control (pathway cause) No No Papp et al., 2006 Introduced in an attempt to control lymnaeid snail vectors of liver fluke (Fasciola gigantica)

Habitat

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The larvae of S. macropus inhabit marshes, swamps, ponds, canals, ditches, slow-flowing streams, and taro and watercress habitats where their snail hosts reside (Davis et al., 1961). The adults are poor fliers and do not move far from the larval habitat, where they can be observed resting on the vegetation, such as grasses and cattail (Typha spp.) (Neff and Berg, 1966).

S. macropus belongs to behavioural group 11 of Sciomyzidae, which are predators of non-operculate snails that live at or just below the water surface, just above the water surface on emergent vegetation, and occasionally those exposed on moist surfaces.

Puparia occur among bits of floating debris or in contact with floating or emergent vegetation, where they are not easily seen and can be mistaken for seeds (Neff and Berg, 1966).

Habitat List

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CategoryHabitatPresenceStatus
Freshwater
Ponds Principal habitat Natural
Rivers / streams Principal habitat Natural

Biology and Ecology

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Reproductive Biology

During copulation the male appositions his forelegs to the antennal styli of the female. It is suggested that mechanosensilla on the styli provide sensory input to the female during mating (Stoffolano et al., 2013).

In the field, females of Sepedon lay eggs near the leaf margins on emergent vegetation, especially on upright grasses, sedges and other longitudinally ribbed vegetation. Only a few eggs are laid at a time, but oviposition occurs at frequent intervals for several weeks (Neff and Berg, 1966). The behaviour of laboratory-reared females of S. macropus during oviposition was described by Neff and Berg (1966). The female raised her abdomen and extruded about two-thirds of the egg, which was held it in this position for 1 or 2 seconds, presumably while she coated the end of the egg inside her abdomen with a small quantity of sperm from her spermathecae. The egg was then placed gently on the substratum and the female touched the lateral surface of the egg and the substratum next to it with the end of her abdomen. The female then raised her abdomen again and laid another egg, which was placed in contact with the first one. The eggs were laid side by side in groups of 9-22 on short sections of cattail (Typha spp.) or grasses. Hatching of the eggs is irregular, with the eggs not necessarily hatching in the order in which they were laid.

Life Stages

In laboratory studies (temperature not reported) using specimens from Central America, the three larval stages lasted a duration of 3­-5, 2-5 and 5-8 days, respectively, pupation lasted 6-9 days and there was a preoviposition period of 3-10 days (average 8.5 days) (Neff and Berg, 1966). Chock et al. (1961) reported a total life cycle of 22-24 days under Hawaiian conditions, comprising 3 days for egg incubation, 11-12 days for the larval period, 7-8 days for pupation and 4 days for the preoviposition period.

Longevity

In laboratory studies (temperature not specified) using specimens collected in Central America, the longevity of five females ranged from 28-155 days, and that of seven males from 41-163 days (Neff and Berg, 1966).

Physiology and Phenology

In Central America and Hawaii, adult S. macropus are active throughout the year. The species is multivoltine with continuous and overlapping generations. Because females breed continuously during the flight season and generally live longer than the time required for a complete life cycle, it is possible to find all life stages of the fly in the same pond at any one period of time (Neff and Berg, 1966).

Mass Rearing

Larvae of S. macropus can be reared in Petri dishes with an adequate food supply to increase breeding stock, but for mass production, redwood troughs stocked with snails were used as aquaria (Chock et al., 1961). The eggs of S. macropus were obtained from adult flies kept in gallon jars containing honey and crushed snails for food, a saturated sponge for water, and grass for resting and oviposition sites. After 2 days the females were moved to a new jar, and pieces of grass on which egg masses were cemented were removed from the jars and floated in the redwood tanks. The emerging larvae did not require any care and once they developed to puparia could be removed from the tanks and placed in the gallon jars for emergence (Neff and Berg, 1966). The occurrence of abnormal specimens of S. macropus was not mentioned in connection with mass rearing projects (Knutson and Vala, 2011).

Laboratory studies have shown that protein material increases both the fecundity and longevity of S. macropus during rearing. Egg production in females reared on brewer’s yeast and honey was much lower than that of flies whose diet was augmented with crushed snails of H. trivolvis (Neff and Berg, 1966). Similarly, Chock et al. (1961) reported that the rate of egg production was 184 eggs for adults reared on a diet of honey and water compared with 14,824 eggs when crushed snails were added to the diet. Chock et al. (1961) also reported that the larvae would feed well on embryonated snail eggs during rearing. Further supplementation of the diet of adults with granular protein hydrolysate resulted in an additional increase in egg production, and the addition of aureomycin to crushed snails fed to the immature larvae was found to decrease larval mortality (Neff and Berg, 1966).

Nutrition

The larvae of S. macropus prey on aquatic non-operculate snails (Knutson and Vala, 2011). In the laboratory S. macropus has been recorded feeding on Australorbis glabratus, Helisoma trivolvis, Physa sp., Lymnaea palustris, Lymnaea humilis and Oxyloma retusa by Neff and Berg (1966) and Lymnaea ollula, Pseudosuccineacolumella and Physa compacta by Chock et al. (1961). The third-instar larvae have also been observed to consume almost entirely the slug Deroceras laeve. Larvae of S. macropus reared in isolation consumed up to 20 snails of H. trivolvis, depending upon the sizes of snails used, and mature larvae were capable of killing snails up to 19 times their own weight (Neff and Berg, 1966).

The food of adult sciomyzids and their manner of feeding are poorly known. The adults of Sciomyzidae are known to feed on decaying animal matter, and more rarely have been seen taking nectar from flowers (Barker et al., 2004). In nature, the adults would be able to feed on snails killed but not entirely consumed by the larvae.  In laboratory studies, adults of S. macropus are able to survive for several weeks by feeding on a diet of honey and brewer’s yeast, but for full egg production during mass rearing a protein supplement is required (see below).

Feeding Behaviour

Larvae of Sepedon are often observed floating just beneath the water surface in ponds and marshes, with their posterior spiracles exposed (Berg and Knutson, 1978; Knutson and Vala, 2011, p. 39). They are not often observed attacking or feeding on snails. They kill the snails quickly and feed upon the fresh tissue, ingesting haemolymph and bits of snail flesh, remaining in the shells only while they feed and then attacking another snail when hungry again. A detailed description of the swimming behaviour of larvae is given in Neff and Berg (1966).

The larva attacks the snail by piercing the exposed foot with its mouthhooks. The snail retracts into its shell and either pulls the larva in with it or the larva follows in quickly. Death of the snail occurs by bleeding and this can take up to an hour for a large snail, depending on the extent of the opening in the haemocoel (Neff and Berg, 1966).

Natural Food Sources

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Food SourceLife StageContribution to Total Food Intake (%)Details
Australorbis glabratus Larval
Deroceras laeve Larval
Erinna newcombi Larval
Fossaria viridis Larval
Helisoma trivolis Larval
Lymnaea humilis Larval
Lymnaea ollula Larval
Lymnaea palustris Larval
Non-operculate snails Larval
Physa Larval
Physa compacta Larval
Pseudosuccinea columella Larval

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Mesovelia mulsanti Predator Larvae/Pupae not specific
Odonata Predator Larvae/Pupae not specific
Pheidole megacephala Predator Larvae/Pupae not specific

Notes on Natural Enemies

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Sciomyzid larvae are attacked by a wide range of predators, such as fish, Odonata, Hemiptera, Coleoptera, planaria and Hydra (Neff and Berg, 1966). In California, the adults are preyed on by generalist predators, such as birds, frogs, toads, spiders, Odonata, robber flies (Asilidae) (Fisher and Orth, 1983). The most common natural enemies of sciomyzids are parasitoid Hymenoptera, particularly ichneumonids, which attack the egg, larval and pupal stages. Both bacteria and viruses are known to attack Sepedon larvae (Neff and Berg, 1966).

Few observations on the natural enemies of S. macropus have been reported. Mass production of S. macropus in outdoor tanks in Hawaii resulted in high levels of predation of larvae and puparia, especially by naiads of dragonflies and damselflies (Odonata) and the hemipteran Mesovelia mulsanti. The ant Pheidole megacephala also robbed containers of larvae and puparia (Chock et al., 1961; Knutson and Vala, 2011).

Means of Movement and Dispersal

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Natural Dispersal

The adults of S. macropus are poor and slow fliers and tend to stay in the larval breeding sites, moving from one resting place to another nearby (Neff and Berg, 1966; Knutson and Vala, 2011).

Intentional Introduction

S. macropus was introduced to Hawaii, USA, from Nicaragua in 1958 for the biological control of lymnaeid snail vectors of the liver fluke, Fasciola gigantica, where it became established (Davis, 1959; 1960).

S. macropus (origin unknown) was later introduced to Guam (date unknown) and became established there (Barker et al., 2004; Knutson and Vala, 2011, p. 141). Papp et al. (2006) reported that S. macropus was introduced to Thailand but no further details were given.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Biological control Yes Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Aircraft Yes Davis, 1959; Davis, 1960

Impact Summary

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CategoryImpact
Economic/livelihood Positive
Environment (generally) Negative

Environmental Impact

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Impact on Biodiversity

As many species of sciomyzid are generalist feeders, their introduction as biological control agents in habitats where they are not native has caused concern that they may attack non-target indigenous species in addition to the intended prey, resulting in biodiversity loss (Barker et al., 2004). Together with habitat loss, predation of the eggs and adults of native Hawaiian lymnaeid snails by both S. macropus and Sepedon aenescens represents a significant threat to their survival. One species of particular concern is Newcomb’s snail (Erinna newcombi), a Threatened species according to the US Endangered Species Act, found only in ten small sites in six watersheds in the mountainous interior of the island of Kauai (US Fish and Wildlife Service, 2004). This species is classified as Vulnerable B1ab(iii) in the IUCN Red List of Threatened Species (Smith and Seddon, 2003).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Erinna newcombi (Newcomb's snail)VU (IUCN red list: Vulnerable); USA ESA listing as threatened speciesUSA/HawaiiSmith and Seddon, 2003

Risk and Impact Factors

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Impact outcomes

  • Threat to/ loss of endangered species
  • Threat to/ loss of native species

Invasiveness

  • Has a broad native range
  • Proved invasive outside its native range
  • Tolerant of shade

Likelihood of entry/control

  • Difficult to identify/detect in the field

Uses

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Economic Value

Eleven species of Sciomyzidae, including S. macropus, have been introduced to Hawaii in attempts to find biological control agents of the lymnaeid snail vectors of the liver fluke, Fasciola gigantica Cobbold (Davis, 1959, 1960; Davis, 1972, 1974; Barker et al., 2004). The liver fluke has been recorded in the Hawaiian Islands since 1892 and is the causative agent of fascioliasis, one of the most important parasitic diseases of beef and dairy cattle there (Davis, 1960).

S. macropus was imported from Managua, Nicaragua, to Hawaii in October 1958 and found to be an effective predator of Fossaria viridis, a non-native lymnaeid snail which is an intermediate host of the liver fluke (Davis, 1960). S. macropus was successfully mass reared in redwood troughs outdoors, producing about 4500 flies per month (Chock et al., 1961; Knutson and Vala, 2011).

Of the species of Sciomyzidae introduced to Hawaii, only S. macropus and Sepedon aenescens (the latter introduced from Japan in 1966 and 1967) became established (Davis, 1974; Knutson and Orth, 1984; Knutson and Vala, 2011). They appeared to be successful in reducing the transmission rate of fascioliasis because the incidence of liver fluke in the livers of slaughtered cattle was found to have dropped in Oahu, Maui and Hawaii between 1966 and 1972 (Davis, 1974) and also on Kauai between 1972 and 1976 (Berg and Knutson, 1978). However, the success of these sciomyzids in controlling fascioliasis has not been assessed since the early 1970s (Barker et al., 2004).

The taxonomy of the lymnaeid snails on Hawaii is confusing. S. macropus is an effective predator of the non-native lymnaeid snail Fossaria viridis (Quoy & Gaimard, 1832), an intermediate host of the liver fluke. Early reports refer to another non-native lymnaeid snail, Lymnaea (Fossaria) ollula Gould, 1859, as being an intermediate host of the liver fluke in Hawaii (Alicata, 1938; Alicata and Swanson, 1937; Davis et al., 1961; Chock et al., 1961), but it is believed these early records are a misidentification of Fossaria viridis (Quoy & Gaimard, 1932) (Morrison, 1968; Cowie, 1997). However, Cowie (1997) states that ollula may be a junior synonym of viridis Quoy & Gaimard, 1932, which has not been formally recognized. Other authors refer to Galba (= Lymnaea) viridis (Quoy & Gaimard, 1832) (Davis, 1972) or Galba viridis (Funasaki et al., 1988), as Galba is sometimes treated as a senior synonym of Fossaria (Cowie, 1997). Knutson and Vala (2011, p. 6) refer to these two species as Austropeplea ollula Gould [Lymnaea ollula] and Austropeplea viridis (Quoy and Gaimard).

Uses List

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Environmental

  • Biological control

Detection and Inspection

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Efforts have been made to trap adults of S. macropus for release in other areas of Hawaii using McPhail traps baited with crushed snails of Lymnaea. The traps were set about 2 feet above the ground or water in swamps or taro paddies where S. macropus had been introduced, and adults were trapped at rates of 50-100 per half hour, many more than could be collected by sweeping (Chock et al., 1961). This technique has proved to be less effective for collecting Sciomyzidae in other areas of the world where monitoring using sweep nets is difficult. The reasons are not clear, but it is possible that baited traps attract Sciomyzidae only for short distances (Neff and Berg, 1966).

Similarities to Other Species/Conditions

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Knutson and Orth (1984) list the various features used to distinguish the Sepedon group from other Sciomyzidae. The larvae of Sepedon and Sepedomerus are similar to those of Sepedonea. The most reliable character to separate these larvae is the dorsal-most accessory tooth of the cephalopharyngeal skeleton; in Sepedomerus and Sepedon the accessory teeth are generally subequal in size and evenly, usually lightly, sclerotized, while in Sepedonea the dorsal-most accessory tooth is larger and more darkly sclerotized  (Freidberg et al., 1991).

In a cladistic analysis, Marinoni and Mathis (2006) concluded that the characters that establish the monophyly of the genus Sepedomerus are: the absence of a postocellar seta; the presence of setation on the mid-femur along the medial surface; the presence of a distinctive seta on the hind tibia along the ventroapical margin; and the size and shape of the male hind femur, which has a height 7.5-8.0 times that of the width and is parallel-sided.

Adults of the Sepedon group appear more slender and elongate than other Tetanocerinae. They are easily recognized in the field by their distinctive body form, posture and habits. They rest on leaves, facing down the vegetation, with their wings laid flat on their backs and their hind legs folded, the tip of the abdomen nearly touching the leaf and the head lifted high, in a characteristic frog-like pose (Neff and Berg, 1966).

References

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Abercrombie J, 1970. Natural history of snail-killing flies of South America (Diptera: Sciomyzidae: Tetanocerini). PhD Thesis., USA: Cornell University.

Alicata JE, 1938. Observations on the life history of <i>Fasciola gigantica</i>, the common liver fluke of cattle in Hawaii, and the intermediate host, <i>Fossaria ollula</i>. Bulletin. Hawaii Agricultural Experiment Station, 80. 22 pp.

Alicata JE, 1953. The snails, <i>Pseudosuccinea columella</i> (Say), new intermediate hosts for the liver fluke <i>Fasciola gigantica</i> Cobbold. Journal of Parasitology, 39(6):673-674.

Alicata JE, Swanson LE, 1937. <i>Fasciola gigantica</i>, a Liver Fluke of Cattle in Hawaii, and the Snail <i>Fossaria ollula</i>, its Important Intermediate Host. Journal of Parasitology, 23:106.

Barker GM, Knutson L, Vala JC, Coupland JB, Barnes JK, 2004. Overview of the biology of marsh flies (Diptera: Sciomyzidae), with special reference to predators and parasitoids of terrestrial gastropods. In: Natural enemies of terrestrial molluscs [ed. by Barker, G. M.]. Wallingford, UK: CABI Publishing, 159-225. http://www.cabi.org/cabebooks/ebook/20043115143

Beaver OP, 1989. Study of effect of <i>Sepedon senex </i>W. (Sciomyzidae) larvae on snail vectors of medically important trematodes. Journal of the Science Society of Thailand, 15(3):171-189.

Berg CO, Knutson L, 1978. Biology and systematics of the Sciomyzidae. Annual Review of Entomology, 23. 239-258.

Boyes JW, Knutson LV, Jan KY, Berg CO, 1969. Cytotaxonomic studies of Sciomyzidae (Diptera: Acalyptratae). Transactions of the American Microscopical Society, 88(3):331-356.

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27/05/2016 Original text by:

Angela Whittaker, Consultant, UK

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